Fluoropolymer fibers are known as friction modifiers in many different end uses. However, fluoropolymer fibers have low tensile modulus and are characterized by low adhesion to other resins; they are relatively high cost products, and some fluoropolymers are characterized by a tendency to cold flow. When used as a friction modifier in industrial applications, such as bearings, fluoropolymer fibers typically take one of the following forms: continuous fluoropolymer filament yarn wound around the surface of an article or part, continuous fluoropolymer filament yarn knitted or woven into fabrics, or continuous fluoropolymer filament yarn chopped into very short floc; this floc is then mixed with a resin and molded into articles or parts.
Although a fluoropolymer staple yarn offers advantages compared to the continuous filament yarn, heretofore, it been has too difficult to make a spun fluoropolymer staple yarn. With a commercially viable spun staple fluoropolymer yarn, yarns and fabrics which use staple fibers having various cut lengths could be designed to meet the needs of industrial friction reducing applications.
Japanese Patent Application HEI 1 [1989]-139833 discloses a fiber material having good flexibility made by mixing less than 30% polytetrafluoroethylene fibers or strands with natural and/or synthetic fibers. Fabrics and clothing made with the fiber material of this publication have both good draping and improved anti-pilling properties.